The present invention is directed to semiconductor processes and devices.
Since the early days when Dr. Jack Kilby at Texas Instrument invented the integrated circuit, scientists and engineers have made numerous inventions and improvements on semiconductor devices and processes. The last five decades or so have seen a significant reduction in semiconductor sizes, which translate to ever increasing processing speed and decreasing power consumption. And so far, the development of semiconductor has generally followed Moore's Law, which roughly states that the number of transistors in a dense integrated circuit doubles approximately every two years. Now, semiconductor processes are pushing toward below 20 nm, where some companies are now working on 14 nm processes. Just to provide a reference, a silicon atom is about 0.2 nm, which means the distance between two discrete components manufactured by a 20 nm process is just about a hundred silicon atoms.
Manufacturing semiconductor devices has thus become more and more challenging and pushing toward the boundary of what physically possible. Huali Microelectronic Corporation™ is one of the leading semiconductor fabrication companies that has focused on the research and development of semiconductor devices and processes.
When fabricating transistors with typical gate dimensions below 50 nm, the so-called “high-k/metal gate” (HKMG) technology has become popular. According to the HKMG manufacturing process flow, an insulating layer included in the gate electrode is comprised of a high-k material. This is in contrast to the conventional oxide/polysilicon (poly/SiON) method, whereby the gate electrode insulating layer is typically comprised of an oxide, preferably silicon dioxide or silicon oxynitride in the case of silicon-based devices. A typical HKMG stack structure can contain a silicon oxide based interfacial layer (IL), a high-k (HK) dielectric, followed by a metal gate electrode. Hf-based dielectrics, HfO2 in particular, are the most widely used high-k dielectrics in current CMOS technology and are usually deposited on top of an IL, whose primary role is to provide good electrical quality of the interface with Si. A sub-nm chemical oxide (SiOx) or oxynitride (SiON) layer is typically employed as IL.
Currently, two different approaches exist for implementing HKMG in the semiconductor fabrication process flow. In the first approach, called gate-first, the fabrication process flow is similar to that followed during the traditional poly/SiON method. Formation of the gate electrode, including the high-k dielectric film and the work function metal film, is initially performed, followed by the subsequent stages of transistor fabrication, e.g., definition of source and drain regions, silicidation of portions of the substrate surface, metallization, etc. On the other hand, according to the second scheme, also known as gate-last or replacement gate, fabrication stages such as dopant ion implantation, source and drain region formation and substrate silicidation are performed in the presence of a sacrificial dummy gate. The dummy gate is replaced by the real gate after the high-temperature source/drain formation and all silicide annealing cycles have been carried out.
A further understanding of the nature and advantages of various embodiments may be realized by reference to the following figures. In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.